a <- seq(1, 17, 2) # a = 1, 3, 5, 7, ..., 15, 17
b <- 3:9		   # b = 3, 4, 5, 6, 7, 8, 9
c <- c(1, 0, 0, 8, 6)	# c = 1, 0, 0, 8, 6
a + c 					# add two vectors
c[c>=3]					# all elements in c > 3
mean(a)					# compute the mean of a
neg_seven <- function(){ return(-7) }
neg_seven()
